1. Field of the Invention
The present invention relates to a negative pressure gauge, and in particular to a negative pressure gauge with a multi-stage positioning means.
2. Description of Prior Art
Conventional digital negative pressure gauge usually includes a body, a crystal liquid screen and an adjustment means. The pressure value of gas flowing through the body is displayed on the liquid crystal screen. The adjustment means is rotated to turn off the liquid crystal screen, so that the liquid crystal screen will not display the pressure value or the pressure value of the gas will be displayed in different units.
Usually, the adjustment means is one that can be positioned at multiple stages. When the adjustment means is positioned at different positioning points, the pressure value will be displayed on the liquid crystal screen in different units or the liquid crystal screen can be turned off. The adjustment means is selectively positioned via a plurality of recesses on a knob and a steel ball, whereby it can be positioned at multiple stages.
However, such a multi-stage positioning adjustment means achieves a multi-stage positioning effect merely by means of the engagement between the plurality of recesses on the knob and the steel ball, so that a user cannot feel clearly the adjustment means being positioned at a certain positioning point. If the user touches the adjustment means erroneously, the adjustment means may be rotated easily so as to change the value displayed on the liquid crystal screen. Thus, this is a problem existing in the multi-stage positioning adjustment means.
Therefore, in order to overcome the above problem, the present Inventor proposes a reasonable and novel structure based on his delicate researches and expert experiments.